PAIN IS ONE OF THE MOST COMMON SIDE EFFECTS of cancer and its treatments. Studies show that up to 50% of cancer patients experience pain, while about 80% of patients with metastatic cancer have moderate to severe pain. For many, opioids offer the most effective way to manage pain. But one of the most common side effects of these drugs is constipation, a condition that can significantly impact quality of life.

Opioids latch on to receptors on cells in the gastrointestinal tract, decreasing the muscle contractions and fluid release needed to have a regular bowel movement. This can cause constipation as well as bloating, pain, discomfort, nausea and vomiting.

“This is a problem for many patients,” says Mehnaz Shafi, a gastroenterologist at the University of Texas MD Anderson Cancer Center in Houston. When on opioids, she says, people can develop a tolerance to the medication, requiring higher doses. But the bowels don’t adapt. “Constipation will not go away or get better,” says Shafi. “You have to educate patients to anticipate this might happen.”

Treatment Options

Talk to your doctor about treatments for constipation.

Constipation affects many cancer patients who take opioids for pain. Different categories of therapies are used to treat constipation. If you are experiencing bowel problems, talk to your doctor about which treatment, or treatment combination, is best for you. Options include:

  • stimulant laxatives like senna or bisacodyl;
  • osmotic laxatives like magnesium hydroxide, polyethylene glycol or lactulose;
  • bulk-forming agents like psyllium fiber;
  • prokinetics like Motegrity (prucalopride);
  • secretagogues like Amitiza (lubiprostone) or Linzess (linaclotide);
  • peripheral mu-opioid receptor antagonists like Relistor (methylnaltrexone) or alvimopan; and
  • opioid receptor agonist and antagonist combination tablets like oxycodone-naloxone.

If cancer patients know that constipation is common, it may make it easier for them to tell their health care provider if they start having bowel problems. “Sometimes a patient is reluctant to tell their doctor they are constipated because they are worried that, if they talk about it, their pain medication will be reduced,” says Louis Liu, a gastroenterologist at Sinai Health System & University Health Network in Toronto.

Liu discussed the categories of treatments available for cancer patients with opioid-induced constipation in an article published in 2016 in Expert Review of Quality of Life in Cancer Care. These range from laxatives and other products that improve bowel function to opioid receptor antagonists, which block the effect opioids have on the gastrointestinal system without decreasing their effectiveness in reducing pain. 

It’s not known which treatments are most effective in cancer patients with opioid-induced constipation. “Most studies are done when new drugs are being developed,” says Liu. “Constipation affects cancer patients’ quality of life, but it is not a high priority for research funding because it is difficult to study.”

The European Association for Palliative Care guidelines for opioid therapy in cancer patients recommend doctors routinely prescribe laxatives with opioids. However, a study published in 2013 that included 2,982 cancer patients in Norway taking opioids for pain relief found only 24.7% received a prescription for laxatives along with their opioid prescription.

Shafi says she recommends patients receive education about the potential need for laxatives at the same time they start opioids. If a problem develops, she says, “treatment can be adjusted to a patient’s needs and symptoms. Generally a combination of two laxative medications from two different categories taken daily is a good idea.”

Cancer patients should be aware that doctors know this is a common problem and that treating it can improve their quality of life. “It would help if doctors asked patients about it,” says Shafi. “But patients should be encouraged to bring up all problems to their physician and nurse,” and that includes constipation.